1. Field of Invention
This invention relates to a multi-color lighting device which employs a group of LED lamps to emit a selectable variety of colors of light. The light is then concentrated by a converging cylindrical lens towards an elongated light beam having a specification azimuth and specification vertical beam width.
2. Prior Art
Typical prior art for a lighting device emitting light having a large azimuthal and small vertical beam width can be found in U.S. Pat. No. 5,224,733 issued to Arimura in which a circular array of a large number of LED lamps direct their diverging light into a linear fresnel lens to create a horizontal light beam throughout the azimuth. Arimura in column 5 lines 49-55 describes a focal circle having a one-inch diameter and eighty LEDs arranged in an array. This array is encircled by a thin linear fresnel lens. The Arimura design only employs a single color. However, even with the single color a quantity of LEDs are employed to approach a uniform intensity throughout the emerging beam.
U.S. Pat. No. 6,048,083 issued to McDermott employs classical lenses in place of the thin fresnel lens of Arimura to concentrate the light from his array of LED lamps. McDermott places the focal point of his LED lamps between the bent focal point of the lens and the interior wall of the lens in order to maximize the efficiency for light concentrated towards the horizontal.
U.S. Pat. No. 5,899,557 issued to McDermott disclosed employing a radial array of LED lamps of a single color encircled by a curved cylindrical surface to concentrate the emitted light into an output beam with a vertical beam width and a large azimuthal beam width. A hollow within the lens is not required in this prior art.
U.S. Pat. No. 4,677,533 issued to McDermott employs a multi-color LED lighting device with a flat lens. There is no curved focal line. There is a circuit FIG. 7 with LED lamps of a variety of colors but no switch for selecting one color and no power control for assuring an established energy level.
Prior art did not provide arrays with curved focal lines and multi-color capability. The above three prior art designs with curved focal lines only disclose a single color. In the current application a multiplicity of output beams each of a different color are required. This requirement of multi-color output presents serious problems for prior art. These problems increase as the uniformity, intensity and beam width of the output beam in each color are required to comply with more difficult specifications. If there are photometric specifications to be met, it is often easy for a lighting device design to comply with a specification when only one color is required and not comply when multiple colors are required. A single color lighting device may have an acceptably uniform and intense emitted beam with each of its LED lamps in a radial array disposed according to prior art. Adding a second plurality of LED lamps of a second color into this array seriously degrades the prior art design resulting in an output beam that will no longer be uniform or of adequate intensity.
Prior art discloses LED lamps in tactile arrays. Most specifications establish minimum intensity requirements within a vertical and azimuthal beam spread. Therefore, lighting devices which emit non-uniform light beams require excessive power as the overall intensity of the emitted beam must be increased in order for all portions of the light beam to meet the minimum requirements. All three of the above prior art patents address this issue by using a plurality of LED lamps placed in a tight array about the center of the lens. Thus, each LED lamp is as close to the geometrical center as possible within the limitation that there are a plurality of lamps in the array. McDermott in U.S. Pat. No. 6,048,083 FIG. 8, Column 12, Lines 37-67 and Column 13, Lines 1-14 discloses his objective to position the LED lamps in a tight array in order to emit light concentrated about the horizontal with minimum loss (divergence) of light.
McDermott in FIGS. 6 and 8, Column 9, Lines 16-25 and Column 13, Lines 7-14 discloses LED types including a spherical body and a wedge base which could be employed to reduce the separation distance between LED lamps. All of referenced prior art disclosed devices using a tight array concept. Unfortunately, this concept cannot be applied if the same array is required to provide multiple colors. All three of the referenced prior art patents would have had a problem providing a lighting device efficiently creating a uniform output beam and additionally of selectively emitting multiple colors. A requirement to emit multiple colors would result in LED arrays with large angular gaps between the LEDs representing each color. If, for instance, Arimura in FIG. 2, Column 5, Lines 50-55 were to require five colors, his array of 80 LEDS would include only 16 LEDs of each color. If the 16 LEDs of one of the selectable colors were lit, then these lit LEDs would not represent the tight array of light emitting LED lamps shown by Arimura. They would in fact have large gaps of unlit LEDs of other colors occupying the space between the emitting LED lamps. Further, each lit LED would be straddled by unlit LED lamps and the bodies of these unlit lamps would intercept and misdirect emitted light as it passes through them. This vast reduction in the number of LEDs of the original color envisioned by Arimura would reduce his light's intensity substantially. In addition, his emitted light beam would become a light beam of greatly varying intensity including hot spots and dim zones. This intensity variation would be problematic in meeting many specifications and lower the efficiency of the device.
Prior art implies using a large focal length relative to the size or outside diameter of the lens and discloses problems relating to the shape of the LED lamp that is used. In McDermott U.S. Pat. No. 5,899,557 Column 10, Lines 57-59, he discloses the objective of increasing distance D2. This is equivalent to increasing the focal length.
In McDermott U.S. Pat. No. 6,048,083, FIG. 10, Column 13, Lines 34-66, McDermott discloses an apparent focal point problem with the T1 ¾ LED lens top lamps that can cause the lighting device to squander light. Specifically, the body of the T1 ¾ LED normally has a lens that refracts emitted light. This refraction creates a plurality of apparent focal points which causes the LED to appear to the lens as an enlarged light source. McDermott offers a spherical top LED as a preferred way to alleviate this problem. The spherical LED, theoretically, does not refract light emitted from the LED element and therefore, theoretically, does not cause the small LED emitter to appear large. This concept does greatly improve the situation but due to manufacturing variations in the spherical contour and placement of the LED element, does not totally eliminate it. Nevertheless, this type of problem is one reason that prior art places its LED arrays at a substantial focal distance (visually observed from the Figures provided in the referenced prior art) from the lens. In general, in order to control the light more effectively, it is desirable to have both a lens with a large focal distance combined with a very small or a point light source. The large focal distance indicated by prior art of variations in light source placement or lens contour. It also reduces the negative consequences relating enlargement of the light source size related to shifting of the apparent point of emission. Since no light source is as small as a point source and since even small light sources can have apparent size enlargements due to refraction at their lens or body, it is usually desirable to have a large focal length to offset these problems. Unfortunately, the large focal length employed by the referenced prior art for a single color device when combined with an array comprising several pluralities of LED emitters each of differing colors, as disclosed in the current patent application, works against designing a lighting device which is compact, efficient and emitting a light beam with uniform intensity throughout a specification azimuth and vertical beam width.
Prior art does not disclose a circuit or switch designed to selectively provide a different power to different colors to obtain a specification required emerging beam for each color. Prior art energized all of the LED lamps within the array equally. This would not be desirable for most multi-color lighting devices. LED lamps of varying colors can have different efficiencies. They can also have different light emitting element configurations and as discussed herein, respond—due to the specific color—differently to the single common lens. The current invention provides a circuit which can deliver selected power to each of the selectable colors by providing a possibly different power to the plurality of lamps representing each color. The current invention can overcome the differences between colors by applying a different power to each color to assure that the emitted light of each color is adequate to comply with the output beam specification.
The referenced prior art teaches or at least implies the following concepts which are taught against in the current invention:                positioning each LED lamp of a color within its array in a close or tactile relationship with adjacent LED lamps of the same color and as close to the center of the lens hollow as possible        having a lens which defines a focal distance which is substantial in magnitude relative to the radius of the LED array        
The referenced prior art teaches the following concepts which are employed in parts of the current invention:                a curved cylindrical surface or a fresnel lens which is formed to provide a curved focal line, bent focal line or a plurality of focal points to provide an emerging elongated light beam having a vertical beam width and a larger azimuth.        a curved array of LED lamps with each lamp having its LED element or the apparent point of emission at the related focal point        a curved array of LED lamps with each lamp having its LED element or the apparent point of emission between its related focal point and the lens        
The referenced prior art does not teach or address the following concepts which are employed in the current invention:                an array or group of LED lamps having a variety of colors each of which includes a plurality of LED lamps        a circuit and switching means capable of selectively energizing each plurality of colors of LED lamps with a dedicated established power level such that emitted light of each color is adequate to comply with a governing specification requirement without excessive power consumption.        a single converging lens disposed and contoured for concentrating light from a plurality of colored LED lamps        an array of ceramic LED lamps each of which comprise a ceramic body capable of withstanding high heat and each being attached to the peripheral edge of a printed circuit board to disperse that heat        disposing a circle of LED lamps each with their apparent point of emission between a plurality of color related focal lines and the lens        a light converging lens having a small back focal length employed to reduce the variations in the focal length and focal circle resulting from color related changes in the index of refraction of the lens.        using ceramic LED lamps without lenses so that a variety of colors will not result in a color related variation in the shifting of the apparent point of light emission within each LED due to its lens. Avoiding color related shifting within each LED resulting from a lens on the LED permits a group of LEDs to be mounted on a circular apparent point of emission line. If the LEDs have lenses or even domes then their apparent point of emission can shift and this shifting will vary in magnitude because it is color related. If LEDs within a color related variation in shifting are then mounted on a circle the surrounding lens will see the emitted light from each LED of a different color at a different location even though all of the LED lamps are physically equal and mounted on a common circle. This variety of apparent points of emission seen by the lens creates misdirected light.        Improving the efficiency while maintaining compliance with some specifications by having a lens with a short focal length in place of the long focal length of prior art.        Improving the efficiency while maintaining compliance with some specifications by having a lens with a short focal length combined with LED lamps devoid of a lens.        